Re: Decibel readings backwards
Totally true... think about playing syncopated rhythyms with the left on snare or even toms while keeping time with your right on hh or ride.
The point of those types of exercises the OP discussed is not necessarily to play lefthand lead fills but to develop your sense of independence between your hands. I think this is especially important with drumset because you need to be able to do all sorts of syncopated grooves with your left hand.
When discussing the concept of inconsistency between your hands, keep in mind that you SHOULD be able to make the sound consistent. If you are playing accent to grace note patterns both your left and right should be able to play the full range of dynamics acurately... Otherwise you'll be relying on your right hand for everything and you'll basically be sacrificing a lot of stuff you could be playing by "copping out" and compromizing to make it easy for your underdeveloped hand.